1. The Field of the Invention
The present invention relates generally to hydrogen production, and more particularly, but not necessarily entirely, to a process and apparatus for producing hydrogen from oil shale.
2. Description of Related Art
The concept of releasing oil from oil shale is well known. “Oil shale” is a naturally occurring sedimentary rock, typically a black or dark brown shale or silt-stone, that is rich in petroleum hydrocarbons, and other materials generally associated with the definition of the broad term “petroleum,” “kerogen” or “bitumen,” from which shale oil can be obtained. The shale oil is produced from the petroleum hydrocarbons, and released from the shale, through pyrolysis, which refers to the subjection of the oil shale to very high temperatures. The petroleum hydrocarbons are released initially in gaseous form. After being cooled they are bituminous-like in form, as they will not flow unless heated to about 400 degrees or more.
Producing commercial quantities of oil from oil shale remains cost prohibitive. The world continues to procure fuel oil by pumping crude oil from natural reserves, and refining the crude. Rapid increases in the price of crude oil, and the continued depletion of our natural oil reserves, may change that.
Large quantities of oil shale reside throughout the world. In the United States, substantial oil shale deposits are found in Colorado, Utah, Wyoming and Texas. The usual process of releasing oil from the oil shale, though it has been cost prohibitive from a commercial standpoint, comprises mining the shale, crushing it, and conducting pyrolysis by subjecting the crushed shale to heat at temperatures of 1000 degrees F.–1400 degrees F. The pyrolysis phase is conducted in the form of “destructive distillation,” a process by which organic substances such as oil shale, wood or coal are decomposed by heat in the absence of air and distilled to produce useful products, in this case, oils. Other products such as coke, charcoal and gases are also the result of destructive distillation.
The liberation of oil from the oil shale by destructive distillation causes considerable coking of the oil shale residue, leaving behind a “retorted oil shale.” The term “coking” refers to the production of coke, which is the solid residue of impure carbon obtained from carbonaceous materials such as oil shale, bituminous coal and the like, after removal of volatile material by destructive distillation.
The phrase “retorted oil shale,” as used herein, is a form of coke, and refers to oil shale that has been subjected to destructive distillation to liberate the petroleum hydrocarbons, or oils, leaving an inorganic residue containing carbon. Therefore, the phrases “retorted oil shale,” “carbon residue,” and “carbon containing material,” as used herein, are related in meaning, and as used herein, are interchangeable.
The phrase “spent oil shale,” as used herein, refers to oil shale from which petroleum hydrocarbons and carbon have been removed.
The term “fluid,” as used herein, shall refer broadly to both liquids and gases.
Attempts have been made in the prior art to improve upon the process of liberating oil from oil shale. Many such attempts are described in the following U.S. patents, which are incorporated herein by reference: U.S. Pat. No. 4,028,222 (granted Jun. 7, 1977 to Prull); U.S. Pat. No. 3,503,868 (granted Mar. 31, 1970 to Shields); U.S. Pat. No. 4,548,702 (granted Oct. 22, 1985 to York et al.); U.S. Pat. No. 4,536,278 (granted Aug. 20, 1985 to Tatterson et al.); U.S. Pat. No. 4,505,809 (granted Mar. 19, 1985 to Brunner et al.); U.S. Pat. No. 4,304,656 (granted Dec. 8, 1981 to Lee); U.S. Pat. No. 3,652,447 (granted Mar. 28, 1972 to Yant); U.S. Pat. No. 3,941,423 (granted Mar. 2, 1976 to Garte); and U.S. Pat. No. 4,357,231 (granted Nov. 2, 1982 to Estes et al.).
It is noteworthy that none of the prior art known to applicant provides an apparatus or method that optimizes the use of heat, and the reactants in the combustion cycle, in a more efficient manner. There is a long felt need for a destructive distillation process applicable to oil shale that is capable of (i) employing a recurring combustion/reaction cycle for a longer period of time by minimizing the presence of nonessential gases, (ii) recovering unused heat instead of permitting the heat to escape into atmosphere, and (iii) reusing and regenerating some of the reactants in the process.
Moreover, there is an increasing need for hydrogen for various uses such as in fuel cells. Fuel cells are electrochemical cells in which the energy of a reaction between a fuel, such as hydrogen, and an oxidant, such as oxygen, is converted directly and continuously into electrical energy. When hydrogen and oxygen react in a fuel cell, water is produced rather than the various pollutants that are generated in combustion of hydrocarbons.
Accordingly, fuel cells are increasingly being used for power generation in both stationary and transportation applications to take advantage of the environmental benefits of fuel cells. It would therefore be an advancement in the prior art to provide a process for extracting hydrogen from oil shale.
The prior art is thus characterized by several disadvantages, or long-felt needs, that are addressed by the present invention. The present invention minimizes, and in some aspects eliminates, the above-mentioned failures, and other problems, by utilizing the methods and structural features described herein.